1. Field of the Invention
The present invention is concerned with new polymers which can be used to form new anti-reflective or fill compositions for use in the manufacture of microelectronic devices. The polymers comprise an alicyclic moiety, with this moiety preferably forming the backbone of the polymer.
2. Description of the Prior Art
The damascene process, or the process of forming inlaid metal patterning in preformed grooves, is generally a preferred method of fabricating interconnections for integrated circuits. In its simplest form, the dual damascene process starts with an insulating layer which is first formed on a substrate and then planarized. Horizontal trenches and vertical holes (i.e., the contact and via holes) are then etched into the insulating layer corresponding to the required metal line pattern and hole locations, respectively, that will descend down through the insulating layer to the device regions (if through the first insulating layer, i.e., a contact hole) or to the next metal layer down (if through an upper insulating layer in the substrate structure, i.e., a via hole). Metal is next deposited over the substrate thereby filling the trenches and the holes, and thus forming the metal lines and the interconnect holes simultaneously. As a final step, the resulting surface is planarized using the known chemical-mechanical polish (CMP) technique, and readied to accept another dual damascene structure.
During the dual damascene process, the contact and via holes are typically etched to completion prior to the trench etching. Thus, the step of trench etching exposes the bottom and sidewalls (which are formed of the insulating or dielectric layer) of the contact or via holes to over-etch which can deteriorate the contact with the base layer. An organic material is therefore used to partially or completely fill the via or contact holes and to protect the bottom and sidewalls from further etch attack. These organic fill materials can also serve as a bottom anti-reflective coating to reduce or eliminate pattern degradation and linewidth variation in the patterning of the trench layer, provided the fill material covers the surface of the dielectric layer.
Fill materials have been used for the past several years which have high optical density at the typical exposure wavelengths. However, most prior art materials have limited fill properties. For example, when the prior art compositions are applied to the via or contact holes formed within the substrate and to the substrate surface, the films formed by the compositions tend to be quite thin on the substrate surface immediately adjacent the holes, thus leading to undesirable light reflection during subsequent exposure steps. Also, because the prior art compositions etch more slowly than the dielectric layer, the unetched fill compositions provide a wall on which the etch polymer will deposit. This etch polymer build-up then creates undesirable resistance within the metal interconnects of the final circuit.
There is a need in the art for contact or via hole fill materials which provide complete coverage at the top of via and contact holes. Furthermore, this material should provide adequate protection to the base of the via and contact holes during etching to prevent degradation of the barrier layer and damage to the underlying metal conductors.
The present invention is broadly concerned with new polymers for use in preparing anti-reflective or fill compositions and methods of using those compositions to protect substrates, and particularly contact and via holes formed therein, during circuit manufacturing.
In more detail, the polymers comprise a moiety according to the formula 
wherein R comprises a light attenuating compound. Preferred light attenuating compounds are those selected from the group consisting of 
wherein each X is individually selected from the group consisting of hydrogen, xe2x80x94OR1, xe2x80x94N(R1)2, and xe2x80x94SR1, and each R1 is individually selected from the group consisting of hydrogen and branched and unbranched alkyl groups (preferably C1-C20, and more preferably C1-C10).
Preferably, the polymer further comprises monomers according to the formulas 
wherein each Y is individually selected from the group consisting of hydrogen, xe2x80x94OH, xe2x80x94CH3, xe2x80x94Cl, xe2x80x94Br, xe2x80x94CN, and xe2x80x94COOR2, wherein each R2 is individually selected from the group consisting of hydrogen and branched and unbranched alkyl groups (preferably C1-C20, and more preferably C1-C10). The polymer should comprise less than about 50% by weight, and preferably from about 1-30% by weight of these two monomers.
Even more preferably, the polymer comprises a moiety according to the formula 
The polymer should comprise at least about 10% by weight, preferably from about 30-95% by weight, and more preferably from about 30-65% by weight of this moiety, based upon the total weight of the polymer taken as 100% by weight.
The weight average molecular weight of the polymer is preferably less than about 100,000 Daltons, more preferably from about 100-30,000 Daltons, and more preferably from about 1,000-5,000 Daltons. The molar ratio of x:y:z should be from about 0:0:0.2 to about 0.8:0.8:1, and more preferably from about 0.01:0.01:0.5 to about 0.5:0.5:1.
Optionally, the above-described monomers can be polymerized with other monomers to alter the properties (e.g., dry etching speed, reflectivity, etc.) of the polymer and of the final anti-reflective or fill composition including the polymer. Examples of such monomers include those set forth in Table 1.
The inventive polymers can be used to prepare anti-reflective and fill compositions by dissolving the polymer in a suitable solvent system. The solvent system should have a boiling point of from about 60-250xc2x0 C., and preferably from about 100-200xc2x0 C. The amount of polymer dissolved in the solvent system is from about 0.1-50% by weight polymer, preferably from about 0.1-20% by weight polymer, and more preferably from about 0.1-20% by weight polymer, based upon the total weight of the composition taken as 100% by weight. The solvent system should be utilized at a level of from about 50-99.9% by weight, preferably from about 80-99.9% by weight, and more preferably from about 90-99.9% by weight, based upon the total weight of the composition taken as 100% by weight.
Preferred solvent systems include a solvent selected from the group consisting of ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, methyl cellulose acetate, ethyl cellulose acetate, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, propylene glycol, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, propylene glycol propyl ether acetate, toluene, xylene, methyl ethyl ketone, cyclopentanone, cyclohexanone, ethyl 2-hydroxypropionate, ethyl 2-hydroxy-2-methylpropianate, ethyl ethoxyacetate, ethyl hydroxyacetate, methyl 2-hydroxy-3-methylbutanoate, methyl 3-methoxypropionate, ethyl 3-methoxypropionate, ethyl 3-ethoxypropionate, methyl 3-ethoxypropionate, methyl pyruvate, ethyl pyruvate, ethyl acetate, butyl acetate, ethyl lactate, butyl lactate, and mixtures thereof.
Preferably, the inventive compositions further comprise a crosslinking agent. This can be accomplished by the use of a crosslinking agent separate from the polymer or, alternately, the polymer can include xe2x80x9cbuilt-inxe2x80x9d crosslinking moieties. Preferred crosslinking agents include those selected from the group consisting of methoxymethyl, methylol, and imino crosslinking agents. The crosslinking agent or moieties should be present in the fill composition at a level of from about 0.1-20% by weight, and preferably from about 0.5-5% by weight, based upon the total weight of all ingredients in the composition taken as 100% by weight. Thus, the fill compositions of the invention should crosslink at a temperature of from about 60-200xc2x0 C., and more preferably from about 60-150xc2x0 C.
It will be appreciated that numerous other optional compounds can be incorporated into the inventive anti-reflective or fill compositions if desired. For example, a light attenuating compound separate from the polymer can be utilized in the composition. Furthermore, a flow promoting agent can be incorporated to increase the flowability of the composition. If a flow promoting agent is utilized, it should be present in the composition at a level of from about 0-30% by weight, and preferably from about 0-10% by weight, based upon the total weight of the composition taken as 100% by weight. Examples of suitable flow promoting agents include phthalic acid derivatives (e.g., dimethyl phthalate, butyl isodecyl phthalate, diethyl phthalate, diisobutyl phthalate, dihexyl phthalate), maleic acid derivatives (e.g., di-n-butyl maleate, diethyl maleate, dinonyl maleate), oleic acid derivatives (e.g., methyl oleate, butyl oleate, tetrahydrofurfuryl oleate), and stearic acid derivatives (e.g., n-butyl stearate, glyceryl stearate).
Also, an adhesion promoter can be added to improve the adhesion between the substrate or photoresist layer and a layer of the inventive composition. If an adhesion promoter is utilized, it should be present in the composition at a level of from about 0.1-5% by weight, and preferably from about 0.1-2% by weight, based upon the total weight of the composition taken as 100% by weight. Examples of such agents include chlorosilanes (e.g., trimethylchlorosilane, dimethylvinylchlorosilane, methyldiphenylchlorosilane, chloromethyldimethylchlorosilane), alkoxysilanes (e.g., trimethylmethoxysilane, dimethyldiethoxysilane, methyldimethoxysilane, dimethylvinylethoxysilane, diphenyldimethoxysilane, phenyltriethoxysilane), silazanes (e.g., hexamethyldisilazane, N,Nxe2x80x2-bis(trimethylsiline)urea, dimethyltrimethylsilylamine, trimethylsilylimidazole), silanes (e.g., vinyltrichlorosilane, xcex3-chloropropyltrimethoxysilane, xcex3-aminopropyltriethoxysilane, xcex3-glycidoxypropyltrimethoxysilane), heterocyclic compounds (e.g., benzotriazole, benzimidazole, indazole, imidazole, 2-mercaptobenzimidazole, 2-mercaptobenzothiazole, 2-mercaptobenzoxazole, urazolethiouracyl, mercaptoimidazole, mercaptopyrimidine), thioureas, and ureas (e.g., 1,1-dimethylurea, 1,3-dimethylurea).
One or more surfactants may be included in the composition to assist in preventing pinholes or striations. If a surfactant is utilized, it should be present in the composition at a level of from about 0.01-1% by weight, and preferably from about 0.1-0.2% by weight, based upon the total weight of the composition taken as 100% by weight. Suitable surfactants include non-ionic surfactants (e.g., polyoxyethylene alkyl (preferably C8-C20) ethers), polyoxyethylene alkyl (preferably C8-C20) allyl ethers, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, and fluorinated surfactants.
The method of applying the fill compositions to a substrate having a contact or via hole simply comprises applying a quantity of a composition hereof to the substrate surfaces forming the hole by any conventional application method (including spincoating). After the composition is applied to the hole, it is preferably heated to its reflow temperature (e.g., from about 60-120xc2x0 C.) during a first stage bake process so as to cause the composition to flow into the contact or via hole(s), thus achieving the desired hole and substrate surface coverage. After the desired coverage is achieved, the resulting fill composition layer should then be heated to at least about the crosslinking temperature of the composition so as to cure the layer.
The degree of leveling (as defined herein) of the cured material in the contact or via holes should be at least about 90%, preferably at least about 92%, and more preferably at least about 95%. The thickness of the cured fill material layer on the surface of the substrate adjacent the edge of the contact or via hole should be at least about 50%, preferably at least about 55%, and more preferably at least about 65% of the thickness of the film on the substrate surface a distance away from the edge of the contact or via hole approximately equal to the diameter of the hole. Finally, the percent of solids in the compositions should be formulated so that the thickness of the film formed on the substrate surface is from about 220-240 nm. Following the methods of the invention will yield precursor structures for the dual damascene process having the foregoing desirable properties.